Mirror support

ABSTRACT

Apart from a frame ( 10 ) that may be formed of parts mutually free to move in translation, the mirror support comprises a lever ( 29 ) suspended from a console ( 28 ) by springs ( 30 ) and position adjustment screws ( 33,34 ) to apply the required orientation with excellent precision; the mirror is attached to this lever. It may be fitted on a rotating tray to put it into the required angular position. This invention is applicable to oscillating laser cavity mirrors because the position of the mirror may be adjusted with extreme accuracy and fixed reliably.

DESCRIPTION

The purpose of this invention is a mirror support, used in particular toadjust the position and orientation of mirrors reflecting a beam in alaser oscillating cavity.

Some lasers comprise a regenerating cavity through which light passes,being reflected in sequence on two mirrors at the ends. These mirrorsmust be oriented with very high precision to reflect the beam in therequired direction. They may be provided with limited reflectingpatterns that define the shape of the exit beam, which also makes itnecessary to perfectly align them along the length of the path of thebeam, by adjusting their side position, or even their angular positionsince their reflecting patterns are usually not circular.

Therefore, the positions of the two mirrors have to be adjusted with agreat deal of care, and thus a search is made for an adjustable mirrorsupport that offers sufficient adjustment precision and sensitivity, andthat is stable and can be immobilized in order to be able to move thecavity without worrying about misadjusting the position of the mirrors.The invention satisfies these needs.

In its most general form, it relates to a mirror support characterizedin that it comprises a frame, a lever suspended from the frame bysprings, a mirror mounting at the end of an arm, the mirror being fixedto the mounting perpendicular to the arm, and two sets of adjustablestops and counter stops sliding through the frame and bearing on thelever, the stop and counter-stop assemblies sliding in the twodirections perpendicular to each other and perpendicular to the leverrespectively, the stops opposing movement of the springs, and the armbeing articulated to the lever at an eccentric position of the lever andarticulated to the frame. For the purposes of the invention, the counterstops are mechanical parts acting in opposition to the stops that areused to retain a part (in this case the lever) between them and thestops at a position defined by the position of the stops. The stops andthe counter stops may consist of sets of opposing screws that may be onthe same center line.

This device is sufficient to orient the mirrors, which is the mostimportant constraint. If it is also required to adjust the alignment ofthe mirrors, then it is advantageous for the frame to comprise a fixedpart, a first mobile part sliding on the fixed part in a firsttranslation direction and a second mobile part sliding on the firstmobile part in a second translation direction and from which the leveris suspended, springs connecting the first mobile part to the fixed partand to the second mobile part, and extending along the first and seconddirections of translation respectively, adjustable stops extendingthrough the fixed part in the first translation direction as far as thefirst mobile part, and through the first mobile part in the secondtranslation direction as far as the second mobile part, respectively,the stops opposing the force applied by the springs, and locking screwsconnecting the first mobile part and extending along the firsttranslation direction and the second translation direction,respectively.

Finally, the angular position of the mirror as it rotates in its plane,can be adjusted if the mounting comprises a part fixed to the arm and arotating tray on the part fixed to the arm, the mirror being fixed tothe tray, and a means of adjusting the angular position of the tray.

Finally, it is advantageous if the stops are adjustment screws and thecounter stops are pressure screws.

An excellent fineness of the orientation adjustment is obtained if eachof the sets of stops and counter stops comprises a stop and counter stopclose to the mounting and a stop and counter stop remote from themounting, and if the arm is articulated to the frame close to the mirrorand to the lever on the opposite side of the mirror and adjacent to thestop and to the counter stop remote from the mounting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to thefollowing figures:

FIG. 1 is a diagrammatic view of a laser cavity,

FIGS. 2 and 3 are general views of the mirror support,

and the other FIGS. 4, 5, 6 and 7 illustrate the mechanical suspensionlever system in more detail.

DETAILED DESCRIPTION OF THE DRAWINGS

A polarized light beam 1 output from a laser arrives at an angle into alongitudinal regenerating cavity 2 (FIG. 1) and a polarizer 3 returns itto a light amplifier 4 and then to a first mirror 5, the reflectingpattern 6 of the first mirror being a square. The beam 1 is reflected inthe opposite direction through the amplifier 4 and the polarizer 3,passes through the polarizer this time without deviation, and finishesby arriving at a second mirror 7 that may be placed at 4.4 meters fromthe first mirror and for which the reflecting pattern 8 corresponds tothe Fourier transform of the square 6 and more precisely to a squaresurface on which striations 9 have been formed crossing each other toform a mesh. The beam 1 is returned by the second mirror 7 towards thefirst mirror 5, but the lens 3 intercepts it and it thus does 50forward-return movements before it exits in its departure direction inthe opposite direction. This large number of forward-return movementsrequires very high precision in the alignment of the two mirrors. Thesupport 60 that will now be described can be used for either of themirrors 5 and 7. FIGS. 2 and 3 show that it comprises firstly a frame 10formed of three parts, namely a plate 11 assumed to be fixed and thatmay be fixed to an inside wall of the cavity 2 by screws not shownpassing through drillings 12 formed through the plate 11; a first movingpart 13 connected to plate 11; and a second moving part 14 connected tothe previous part; connections between the three parts of the frameconsist of ball bearing races 15 and 16 along which the first movingpart 13 slides in the transverse direction on plate 11 and the secondmoving part 14 slides in the vertical direction on the first part 13. Anadjustment screw 18 is engaged through a lug-shaped portion 19 mountedon the plate 11, and its free end reaches a thrust face 20 of the firstmoving part 13 and pushes it when screw 18 is turned; a spring 21opposing the screw 18 connects the thrust face 20 to the lug 19 andbrings them together to form the stop for the screw 18. This system iscapable of precisely and accurately adjusting the transverse position ofthe first mobile part 13 and consequently also of the second mobile part14; there is also another screw 22, that is a pressure or clampingscrew, engaged in the thrust face 20 that passes through the lug 19;screwing it tends to bring the thrust face 20 closer to the lug 19 andtherefore locks the first mobile part 13 onto the plate 11 by holdingthe stop of screw 18, tightened slightly to prevent maladjustments butwithout introducing mechanical constraints that could deform the partsexcessively and distort the adjustment previously obtained using screw18. The system remains perfectly stable even if the mirror support ismoved afterwards. A similar system exists to bring together the twomobile parts 13 and 14 towards each other and to adjust their positionin the vertical direction; the result is a threaded adjustment screw 23passing through a lug-shaped portion 24 of the first mobile part 13 andpressing on a thrust face 25 of the second mobile part 14, a spring 26tensioned between the lug 24 and the thrust face 25, and a clampingscrew 27 capable of pulling the mobile parts 13 and 14 towards eachother at the location of the lug 24 and the thrust face 25 to hold thestop in place.

The second mobile part 14 supports a console 28 with a straight squaresection vertically above the plate 11 over a fairly long length and thatcontains a lever 29, that cannot be seen in FIG. 2, and that forms anessential part of the invention. It extends approximately perpendicularto the two displacement directions of the mobile parts 13 and 14, likethe console 28, and it is suspended from the console by a pair ofsprings 30 laid out obliquely. The console comprises mechanical systemssimilar to the previous systems to adjust the position of the lever 29in the form of two identical groups 31 and 32 and placed at its ends(FIGS. 4 and 5); each comprises a first adjustment screw 33 engagedthrough the console 28, the free end of which is supported on the lever29, a second adjustment screw 34 arranged in the same way butperpendicular to the previous screw, and two other screws 35 and 36 thatare pressure screws engaged through a stirrup 37 in the console 28 andthat come into contact with the faces of the lever 29 opposite the faceson which the screws 33 and 34 are stopped respectively. Since screws 35and 36 are on the same center lines as screws 33 and 34 respectively onthe other side of lever 29, a cross-shaped assembly is used in whichscrews 33 and 34, opposing the action of the springs 30, are used toadjust the position of the lever 29 and the screws 35 and 36 are counterstop screws that hold the lever 29 firmly in place at the previouslychosen position by exerting a slight clamping force; their action isequivalent to the action of the pressure screws 22 and 27 mentionedabove. Finally, other pressure screws with references 38 are engaged inthe console 28 and their ends bear on the side of screws 33 and 34respectively to hold them in place despite possible vibrations.

Rotation of screws 33 in one group 31 or in the other group 32 willcause tilting of the lever 29 in a plane, and rotation of screws 34 willtilt lever 39 in another plane perpendicular to the previous plane; itis clear that tipping of these levers will rotate mirror 5 or 7 in thesame directions.

Lever 29 is attached through a universal joint 53 to an arm 39 thatprojects forwards to extend through openings in the mobile parts 13 and14 to end at a mounting 40 of the mirror, projecting at the end of frame10. The mounting 40 is composed of a fixed part 41 fixed to the arm 39and a plate 42 laid out on the fixed part 41 so that it can rotate(FIGS. 2, 4 and 6); it is held in place on the fixed part 41 by arotating drum 48, by screws 43 fitted into oblong holes 44 in the plate42 and which therefore enable an angular movement of the plate; a cam 45is held in place in a radial groove 46 in the plate 42 and if it isrotated (possible using a screwdriver), causes the plate 42 to rotate onthe fixed part 41; therefore the angular position of the mirror 5 or 7can be adjusted. The mirror, for example 5, may be glued to the bottomof a compartment 47 at the center of the plate 42, while being directedto the opposite end of lever 29.

The mounting 40 may be supported by the second mobile part 14 through auniversal joint mechanism comprising a ring (49) (FIG. 7) that enablesrotations imposed by groups of stops 31 and 32 while reducing the forceapplied on the springs 30 due to part of the weight of lever 29 and theparts connected to it; the ring 49 is housed in an opening 50 of thesecond mobile part 14, like the mounting 40; it is connected to thesecond mobile part 14 by a first pair of balls 51 aligned horizontally,and to the fixed part by a second pair of balls 52 aligned vertically;the alignment directions of the pairs of balls 51 and 52 correspond tothe pivot axes of the ring 49 and the mounting 40, which thereforefreely moves into the required orientation.

The universal joint 53 between the lever 29 and the arm 39 isconstructed in the same way as the previous universal joint as can beseen in FIGS. 5 and 7. Since it is opposite to mirror 5, a normal methodof adjusting the mirror orientation will consist firstly of acting onscrews 33 and 34 in group 31 adjacent to the joint 53 such that thescrewing depth is applied to it perfectly, and that a relatively largerotation is transmitted to the arm 39; a screwing action can then beapplied to the screws 33 and 34 in the other group 32 to make the lever29 pivot about the screws 33 and 34 of the first group 31; the universaljoint 53 will only move slightly, which is acceptable for making a fineadjustment to the orientation of the mirror 5 by rotating the arm 39slowly.

What is claimed is:
 1. Mirror support characterized in that it comprisesa frame (10; 11, 13, 14; 28), a lever (29) suspended from the frame bysprings (30), a mounting (40) for the mirror (5) at the end of an arm(39), the mirror being fixed to the mounting perpendicular to the arm,and two sets (33, 35; 34, 36) of adjustable stops and counter stopssliding through the frame (28) and bearing on the lever (29), thecounter-stops (35, 36) opposing the stops (33, 34) through the lever,the stop and counter stops sliding in the two directions perpendicularto each other and to the lever respectively, the stops opposing movementof the springs, and the arm being articulated to the lever at aneccentric position of the lever and articulated to the frame.
 2. Mirrorsupport according to claim 1, characterized in that each of the stopsand counter stops are respectively provided in a first assembly close tothe mounting and a second assembly remote from the mounting along thearm.
 3. Mirror support according to claim 1, characterized in that theframe (10) comprises a fixed part (11), a first mobile part (13) slidingon the fixed part in a first translation direction and a second mobilepart (14) sliding on the first mobile part (13) in a second translationdirection and from which the lever (29) is suspended, springs (21, 26)connecting the first mobile part to the fixed part and to the secondmobile part, and extending along the first and second directions oftranslation respectively, adjustable stops (18, 23) extending throughthe fixed part in the first translation direction as far as the firstmobile part, and through the first mobile part in the second translationdirection as far as the second mobile part, respectively, the stopsopposing the force applied by the springs, and locking screws (22, 27)connecting the first mobile part and extending along the firsttranslation direction and the second translation direction,respectively.
 4. Mirror support according to claim 1, characterized inthat the stops (18, 23, 33, 34) are adjusting screws.
 5. Mirror supportaccording to claim 1, characterized in that the counter stops (35, 36)are pressure screws.
 6. Mirror support according to claim 1,characterized in that the mounting (40) comprises a part (41) fixed tothe arm (29) and a rotating tray (42) rotating on the part fixed to thearm, the mirror being fixed to the plate, and a means (45) of adjustingthe angular position of tray.
 7. Mirror support according to claim 6,characterized in that the means of adjusting the angular positioncomprises a cam (45) in a groove (46) in the tray (42).
 8. Mirrorsupport according to claim 1, characterized in that it comprises amounting (40) of the mirror pivoting in the frame (14) through a ring(49), the ring pivoting in the frame about the first axis and themounting pivoting in the ring about a second axis perpendicular to thefirst axis.
 9. Mirror support according to claim 2, characterized inthat the arm (39) is articulated to the frame close to the mirror (5)and to the lever (29) opposite the mirror, adjacent to the stop and thecounter stop (31) remote from the mounting.